Just watched the movie, is not that bad, I'll give it a 4.5/10. The story was meh, Damian was kinda overpowered, the voices were terrible and the dialogue was lame. I kinda enjoyed the movie, but the thing that mostly bothered me was Deathstroke's character. They completely destroyed it, like Darkseid in JL: War. Jobberstroke Deathstroke was beaten by Damian, pwned by Batman, and... Damian again. He also lacked intelligence, and had basically no motivation... If they'd done him well, I'd probably give it a 5 or even a 6.
DC is not the same... Although Assault on Arkham looks really good if you ask me, I hope they don't screw up.